Originally Posted by AF
The header from your B16 won't bolt up to a B18C5, you'll need a new one. The collector should be okay, but ideally go with recommended size.
It will bolt up, however the length of the header or cat may be different causing problems underneath. If you want to use your current header, keep your current cat and exhaust, and it should all bolt up. The bolt pattern on all BSeries heads are the same- its just a matter of whether or not it matches up on the underside.